Continuously running rolling mill for producing tubes



Sept. 10, 1940. F, og s I 2,214,279

CONTINUDUSLY RUNNING ROLLING MILL FOR PRODUCING TUBES Filed June 15, 1958 v 2 Sheets-Sheet 1 Fly. 1

Inventor ULiW" A ttomey.

F. KOCKS CONTINUOUSLY RUNNING ROLLING MILL FOR PRODUCING TUBES 2 Shaets-She'et 2- Filed June 15, 1938 Inbentor .7. .jfocko by m g W4 Attorney.

Patented Sept. 10, 1940 UNITED STATES PATENT" OFFICE CONTINUOUSLY RUNNING ROLLING MILL FOR PRODUCING TUBES Fritz Kocks, Dusseldorf, Germany, assignor to Demag Aktiengesellschaft, Duisburg, Germany, a corporation of Germany Application June 15, 1938, Serial No. 213,735

Germany June 21, 193"! 9 Claims.

Up to the present the method adopted of producing seamless tubes in continuously operating rolling mills has been to place a pierced, hollow billet having a wall of varying thickness on a cylindrical mandrel rod and to pass the billet through a number of rolling mills disposed one behind the other; then to loosen the rolled billet in rolling mills provided for the purpose or to draw the billet off on suitable stripping apparatus. At present the continuously running rolling mills are so constructed that ordinary twohighrolling frames are used which are disposed alternately in staggered relation at determined angles. In the older rolling mills of this type that were produced about 30 years ago in Germany (the Fassel rolling mill) the drive of for example 7 passes disposed one behind the other was efiected by a common fixed spur gear laid out from pass to pass to correspond tothe rise in speed of travel of the rolled metal. The vertical rolls were driven from the spur gear by means of bevel gearing. The two rolls of the individual frames were coupled to the fixed gearing by spindles and coupling sleeves. The disadvantage always involved in this arrangement was that by providing an unvariable and common spur gear for driving the rolling mill, the speed of the roll in each frame was fixed so that it was not possible to provide variation in speeds I by making use'of different diameters of rolls.

vThe rolls of these rolling mills were constructed of a diameter that was about four times as great as that oi. the metal billet being rolled, and the pass was 'so formed that the considerable spread ing of the metal being rolled. was taken into account by a correspondingly large lateral opening 1 in the pass. I 1

Furthermore the roll frames in this early type of continuously running rolling mill were so constructed that a common roll frame was made for alhseven passes in order to maintain the distance from pass to pass as small as possible and to limit the dimensions. of the spur gear;

The rolling speeds once determined led to calibration of the rolls could not beadJusted to the practical shaping needs of the moment. In 1 those unavoidable cases of breakdown in which a a billet becamewedged in the rolling mill during the working operation, the working of the mill had to be interrupted for whole workingshifts for the purpose of removing the obstruction.

' A further disadvantage of using these rolling mills was. that it wasnot possible to produce 'tubes with thinwalls. It was even found necesvery considerable working difliculties because the of each individual frame to practical shaping I requirements. The frames, as in the case of the .first mentioned rolling mill, are two-high and the rolls used are likewise the. same.

The present invention is based on the generally known fact that a roll stretches the metal lengthwise more easily and widens it less the shorter the effective space between the rolls, that is to say the smaller the diameter of the working rolls. Furthermore a tubular body can be more easily stretched lengthwise according as the shaping tools engage-more evenly the periphery of the tube. The last consideration led to the use of more than two working rolls to each pass. If however more than two working rolls are employed to each pass it is necessary to take so muchmore care that the metal being rolled does not widen' out inadmissably and thereby be pressed into the space between the working rolls and cause the formation of seams on the tubes.

Widening or spreading of the metal being rolled depends upon the ratioof length to breadth of the space between the rolls. The longer ,this space, the greater is the tendency of the metal to widen out or spread. Since however as the number of working rolls increases per'pass the 'widthof the slot between the rolls is reduced, and thus the tendency of the metal to widen out orspreadincreases, care must be taken, partic 'ularly' when using more-than two working rolls to each pass, that the length of the space between the rolls is maintained small, in order that the ratio of length to breadth of the space between the rolls that is involved in the'spreading' or widening of the metal being rolled shall be as favourable as possible. The diameter of. the

working rolls must therefore be as small as possible. The-invention gives as the scale for the determination of the measurements of the working rolls, the ratio of diameter of rolls to .diameter of metal being rolled. of 2-: 1 asthe uppermost limit that may be .used, while a smaller ratio must if possible be used. From the foregoing considerations it follows however that the attempt to shape the periphery of the tube as evenly as possible must not be carried too far, for if it were desired to bring into use a very large number of working rolls in such a rolling mill, the result would be that with the same reduction in cross-section of the metal being rolled, the breadth of the space between the rolls will become smaller and smaller on each working roll, that is to say the ratio of length of the space to the width becomes more and more unfavourable and the tendency of the metal to widen out or spread, or in other words to produce seams on the tubes, increases. For this reason the invention is intended to be confined to the use of three working rolls.

The limitation of the number of working rolls to three for each pass is however advantageous for a different reason. Whereas when using more than three working rolls of smaller diameter for each pass, only a bearing for each roll at one end or side is practicable, the use of three working rolls provides the possibility of a twoended bearing for the working rolls and further the possibility of an advantageous coupling of the-rolls to the driving gear. The two-ended bearing for the working rolls is of special importance to the present invention because in view of the thin working rolls only thin roll journals can be employed and therefore only an eilicient bearing can support the high rolling pressure.

The invention thus consists in the use in a continuously operating rolling mill of the type hereinbefore described of roll frames with three driven working rolls in bearings at both ends, for producing tubes with thin walls, the radius of the working rolls being measured in the base of the pass, the maximum radius being equal to the diameter of the metal being rolled.

The invention furthermore provides an indication for determining the number of the passes thatbe considered as the most eifective in a continuously operating rolling mill of the kind hereinbefore described. The basis is that the length of the space between the rolls is a function of the amount by which the metal being rolled is reduced in one pass. The greater the amount of reduction, the greater also is the widening-out or spreading of the tubes. It follows that the reduction in each pass must not be too great. Whereas in the old constructions of continuously operating tube rolling mills, the length of the hollow body was increased four times in seven passes, working rolls being employed that, as described, had about four times the diameter of the metal being rolled, according to the invention the number of passes is always at least equal to three times the elongation factor. The elongation factor is the ratio of initial cross-section of the hollow billet to the cross-section at the end of the finished tube. If the hollow billet is to be stretched for'example, to double its length, six passes must be made. If the amount of stretch is to be four times as much, twelve passes must be made.

Further features of the invention that are concerned with producing the rolling mill hereinbefore described in a particularly simple manner and that are especially advantageous structurally are set forth in the description following, in which examples of a rolling mill according to the invention are described by reference to the accompanying diagrammatic drawings,

Figures 1 and 2 show a complete rolling mill according to the invention.

Figures 3 to 5 show end elevations of two different constructions of the roll frames.

Figure 6 is a corresponding side elevation.

Figure 7 is a longitudinal sectional elevation on an enlarged scale of the bearings and couplings.

Referring to Figures 1 and 2 on a foundation frame or base plate' A are mounted the roll frames BI to BIO. As will be seen from Figure 1 a certain amount of space is left between the roll frames, for the reason hereinafter appearing. Each of the roll frames BI to BIIl has its own driving motor CI to CID respectively, driving for example through transmission gearing DI to DIII respectively on to the respective coupling journals El to Elli of the driving shafts of the frames.

Each roll frame casing or housing I (Figures 5 and 6) consists of a hollow body formed of plate members, which as shown in Figure 6 is provided at its sides with bracket-like extensions 2, by means of which it is supported on the foundation frame or base plate A and is securely held on the latter by means represented by the part 3.

The foundation frame or base-plate A is trough-shaped; its side walls are provided with recesses or cavities 4 to receive the lower parts of the roll frames. In accordance with structural requirements the roll frame casing or housing I is in two or more parts. A bipartite construction of the frame casing or housing that satisfies the conditions hereinafter described is illustrated in Figure 6 by the joint 5.

In order that the rolls of the roll framesshall be readily interchangeable, the sets of rolls are according to the invention mounted in the easings I in interchangeable frames 6. The frames 6 (Figures 3 to 5) are inserted in the axial direction of the'pass through holes in the walls of the casings or housings I and there secured. The rolls 8 are mounted with their journals at both sides carried in projecting jaws I. on the interbevel gear wheels-I6 mounted respectively on shafts I3, I4 and I5. These three shafts, which are disposed at right angles to each other, are

positively connected together by pairs of bevel gear wheels I1, I! and I8, I8. The bevel gear wheel drive I8, I8 is engaged by the main driving shaft I9, which is coupled to the corresponding transmission gears D1 to D1o in the manner hereinbefore described.

As hereinbefore stated, the exchange of the rolls by the use of the interchangeable frames 6 as supports for the working rolls is very simple. To enable the rolls to be removed, the coupling sleeves I! are moved along until either the journal 9 or the journal II is released. Thereupon the interchangeable frame 6 is disconnected from the casing or housing I; the interchangeable frame 6 can then be withdrawn with the rolls fitted therein in the direction of the axis of the pass from the casing I and while suspended in the manner shown in Figure 4 from the carrying device III constructed as guide members for the axial moveof a hoist be then lifted out. The fitting of the I, the distance members 22 (Figures 4 and 5),

which are required between the frames for absorbing the pull or pressure during rolling, are

ment of the interchangeable frames. The spacing of the frames is necessitated by the assembling and dismantling of the interchangeable frame in the axial direction as hereinbefore described.

The construction according to Figure 5 differs from that according to Figures 3 and 4 in the fact that the pairs of bevel gear wheels l2, l8, and the shafts II that are tobe coupled to the roll journals 9 are not mounted directly on the casing I, but on members 23, 24 and 25 which are adapted to move in'the casing I. The bevel gear wheels ltxare at the same time capable of movement .on the stationary shafts l3, H and IS. The members 23, '24 and 25 can be moved by means of the handwheel 26 and the spindle 21 in such manner that the distance between the axes of the shafts H and the axis of the pass can be varied.

As will be seen from Figure 5 the spindle .21 may be provided to engage the sliding member 25 through the intermediary of a movable wedge 28 if the structural conditions render direct coupling of the sliding members to the spindle difficult. The shafts H are provided capable of movement in order to enable interchangeable frames-with rolls ofdifferent diameters to be used without its being necessary to span appre- (liable angular variations with the clutch sleeves Whereas in rolls mounted at both ends the rolls and their journals consist usually of the same basic metals, the roll bodies 8 are drawn over the shafts 9 in'the form of rings in the rolling mill according to the invention, as is shown in Figure 1. Thus. for each of the members 8 and 9 it is possible to use that metal with the most suitable hardness and surface qualities for the pu'rposefor which the said members are intended. The bearing journals of the shafts! are hardened at the parts'that form the bearing so that the quality of the bearing is much improved. Furthermore, having regard to the small diameter of the journals the coupling between the roll journals 9 and the ends of the shaft H are provided as a toothed coupling. The coupling ends of the journals 9 and l I are for the purpose provided with teeth 9a and Ila respectively. .The teeth of one of the journals are provided of such a length that the coupling sleeve it provided with corresponding internal teeth can be moved in one direction such a distance that one journal is released from the coupling sleeve. As hereinbefore described this is necessary to enable the interchangeable frames 6 to be assembled and taken down. As the toothed coupling cannot bridge any appreciable angular variations, and therefore the axes of the journals 9 and H must be in alignment as nearly as possible, the construction according to Figure 5 has special importance with shafts II that can be moved at a distance from the axis of the pass.

It will be understood that the construction may be such that in each of the casings or housings i two interchangeable frames 6 are provided disposed at the two faces of-the casing or housing so as to be capable of being inserted and correspondingly the driving means described for one set of rolls are provided in duplicate in the casings or housings I. The two interchangeable frames are advantageously so staggered in the casing or housing I that the meeting edges or surfaces of the rolls of one pass do not lie immedimetalbecome wedged in a rolling mill during the rolling operation for any reason, such as breakage due to faulty material or by fracture due to poor adjustment of the speeds of the rolls of individual frames, the-use of interchangeable frames enables all the interchangeable frames to be moved out over the guide members 22 between the casings or housings by the use of a suitable mechanical device and all the passes with the mandrels inside lie outside the ,roll mill frames. In this way it is very easy torectify breakdowns.

' Instead of mounting the rolls in interchangeable frames which can be moved into stationary roll frames, the individual roll frames can be constructed as interchangeable frames. In such case the interchangeable frame contains the driving elements for the three working rolls so that the driving power can be supplied by a. single coupling journal to all three working rolls of a'frame. In this case a stationary spur gear with driving motor is used for each single roll frame, the coupling journals between thestationary gearing and the interchangeable frame being so provided that the ready interchangeability of the interchangeable frames is left unaffected. In order to enable the frames to be quickly changed it is proposed that theinterchangeable frames shall not as heretofore be secured on to a foundationframe or base-plate by means of tie-bolts, but they can be secured to acommon foundation frame or base-plate by means of suitable mechanical or hydraulic clamp 'block is pierced in askew rolling .mill to produce a log billethaving as-thin walls as possible. This billet is fed on a cylindrical rod to the continuous frame, and then, after leaving the continuous train passes through a loosening rolling mill and is removed from the mandrel beyond the loosening rolling mill. The loosening rolling mill may be so constructed that it becomes a pass rolling mill similar in construction to the continuous frames, but with diameters of rolls that are at least four times as great as the diameter of the rolled metal and whose calibration presents large lateral openings. By reason of this large diameter the widening or spreading that is undesirable in a continuously operating rolling mill is produced and by this means the tube is readily loosened from the mandrel and by simple means removed therefrom.

As. compared with all known continuously operating tube rolling mills it is possible with such a rolling mill to shape the tube after it has been withdrawn from the mandrel rod in a reducing rolling mill without further heating. The whole rolling process proceeds so rapidly that any cooling of the tube is avoided in all circumstances. Having regard to the fact that such a rolling mill enables very thin walled small tubes to be produced it is possible to produce by heating from the solid billet small gas tubes of for example diameter.

1. In acontinuously operating rolling mill for producing thin-walled tubes from thicker-walled billets by rolling out the billets over a cylindrical mandrel comprising a plurality of roll frames and in each of these roll frames a set of working rolls, these working rolls being driven and forming a pass, the use of sets of working rolls comprising three working rolls, each of these rolls being supported in a bearing at each end of the roll, the radius of the working rolls, measured in the base of the pass, being at its maximum equal to the diameter of the metal being rolled.

2. A continuously operating rolling mill according to claim 1, in which the number of sets of working rolls, each presenting a working pass, is at least three times as great as the elongation factor, the elongation factor representing the ratio of the cross-section. of the hollow billet at its front end to the cross-section of the-finished tube at the ends.

3. A continuously operating rolling mill according to claim 1, in which interchangeable frames are provided to carry the working rolls and are mounted in the individual roll frames so as to be readily removable and replaceable.

4. A continuously operating rolling mill according to claim 1, provided with toothed wheels for driving the working rolls and means for 6. A continuously operating rolling mill. ac-- cording to claim 1, providing with working rolls of a form comprising a body of annular shape and a spindle of suitable form to receive the body of annular shape thereon in fixed position,

the roll spindles being provided with journals that are in the form of toothed coupling elements.

7.-A,, continuously operating rolling mill according to claim 1, provided with working rolls having spindles, the bearing journals of which are hardened, ground .and polished.

8. A continuously operating rolling mill for producing thin walled tubes from thicker walled billets by rolling out the billets over a cylindrical mandrel, comprising a plurality of roll frames associated in a series and through which frames each billet passes in succession, at least one interchangeable frame mounted in each roll frame and three driven working rolls forming a single pass mounted in each interchangeable frame, the said frame being provided with bear- 5 ings for each roll at each side ofthe said roll, and driving elements in the said interchangeable frames applied to each of the said rolls, and driving means in the roll frames, the said driving means being detachably coupled with the said driving elements for the transmission of a drive to the said rolls.

9. A continuously operating rolling mill according to claim 1, provided with a foundation base in which the roll frames are disposed in position in series and clamping devices for securing the said roll frames in the said foundation base.

FRITZ KOCKS. 

